System and Method for High Efficiency Wireless Local Area Network Communications

ABSTRACT

System and method embodiments are provided for high efficiency wireless communications. In an embodiment, a method in a network component for transmitting a frame of two different fast Fourier transform (FFT) sizes includes generating a frame, wherein the frame comprises orthogonal frequency-division multiplexing (OFDM) symbols in two different FFT sizes, wherein the frame comprises a first portion and a second portion, wherein the first portion comprises a first FFT size and the second portion comprises a second FFT size; and transmitting the frame during a single transmission opportunity.

PRIORITY CLAIM AND CROSS-REFERENCE

This application claims the benefit of the following provisionally filed U.S. patent application: Application Ser. No. 61/903,134, filed Nov. 12, 2013, and titled “System and Method for High Efficiency Wireless Local Area Network Communications,” which application is hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a system and method for wireless communications, and, in particular embodiments, to a system and method for high efficiency wireless local area network communications.

BACKGROUND

In 2013, the Institute of Electrical and Electronics Engineers (IEEE) formed the IEEE 802.11 high efficiency wireless local area network (WLAN) (HEW) study group in order to enhance the efficiency and performance of WLAN deployments. The HEW study group is considering the improvement of spectrum efficiency to enhance the system throughput/area in high density scenarios of access points (APs) and/or stations (STAs). However, legacy devices may not be able to utilize the new features. Therefore, it may be desirable to have systems and methods for allowing both legacy devices and HEW compliant devices to both communicate in the same wireless network.

SUMMARY

In an embodiment, a method in a network component for transmitting a frame of two different fast Fourier transform (FFT) sizes includes generating a frame, wherein the frame comprises orthogonal frequency-division multiplexing (OFDM) symbols in two different FFT sizes, wherein the frame comprises a first portion and a second portion, wherein the first portion comprises a first FFT size and the second portion comprises a second FFT size; and transmitting the frame during a single transmission opportunity.

In an embodiment, a wirelessly enabled network component includes a processor and a computer readable storage medium storing programming for execution by the processor, the programming including instructions to: generate a frame, wherein the frame comprises orthogonal frequency-division multiplexing (OFDM) symbols in two different FFT sizes, wherein the frame comprises a first portion and a second portion, wherein the first portion comprises a first FFT size and the second portion comprises a second FFT size; and transmit the frame during a single transmission opportunity.

In an embodiment, a wireless system includes a transmitter; and a processor coupled to the transmitter, wherein the processor is configured to generate a frame, wherein the frame comprises orthogonal frequency-division multiplexing (OFDM) symbols in two different FFT sizes, wherein the frame comprises a first portion and a second portion, wherein the first portion comprises a first FFT size and the second portion comprises a second FFT size, and wherein the processor is further configured to cause the transmitter to transmit the frame during a single transmission opportunity.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:

FIG. 1 illustrates a network for communicating data;

FIG. 2 illustrates various IEEE 802.11 architectures;

FIG. 3 illustrates a mixed OFDMA frame format with a HEW-data portion having a numerology that may be different from the legacy WLAN portion;

FIG. 4 illustrates a mixed OFDMA frame format with STBC based frame control symbols;

FIG. 5 is a flowchart of an embodiment of a method for generating a frame with a mixed OFDMA frame format;

FIG. 6 is a flowchart of an embodiment of a method for decoding a frame that includes a mixed OFDMA frame format;

FIG. 7 is a flowchart of an embodiment of a method for decoding with a legacy wireless device a frame that includes a mixed OFDMA frame format that includes a first portion of a frame in a first FFT size or numerology format and a second portion of the frame in a second FFT size or numerology format; and

FIG. 8 is a block diagram of a processing system that may be used for implementing the devices and methods disclosed herein.

Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the presently preferred embodiments are discussed in detail below. It should be appreciated, however, that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention.

High efficiency WLAN (HEW) has the potential to provide improved area throughput and cell-edge performance, collaboration rather than coexistence between neighboring basic service sets (BSSs), and the use of spectrally efficient modulations, e.g., orthogonal frequency division multiple access (OFDMA) and its associated scheduler for enhanced quality of service/quality of experience (QoS/QoE).

Disclosed herein are systems and methods for transmitting data in a wireless network that includes a frame with mixed frame format with a first portion that includes a legacy frame format and a second portion that includes a HEW-data format. The first portion may be a preamble that is decodable by both legacy devices and newer devices that are HEW compliant.

Disclosed herein is an embodiment of a method in a network component for transmitting a mixed frame of wherein the mixed frame includes two segments each with a different fast Fourier transform (FFT) size from the other. The method includes generating a frame, wherein the frame comprises orthogonal frequency-division multiplexing (OFDM) symbols in two different FFT sizes in a mixed frame format, wherein the frame comprises a first portion and a second portion, wherein the first portion comprises a first FFT size and the second portion comprises a second FFT size; and transmitting the frame during a single transmission opportunity. In an embodiment, the first portion includes a preamble in a legacy format. In a method, according to one example embodiment, the frame includes a first field and a second field, and wherein the first field provides information for automatic gain control (AGC) and synchronization and the second field provides information for synchronization and channel estimation. In an embodiment, the first portion includes a first field and a second field that provide information enabling a receiver to estimate two stream channels for two stream space-time block code (STBC). In an embodiment, the first portion includes a frame control field and wherein the frame control field comprises two symbols causing a legacy device to stop decoding the frame when encountered by an auto-detection mechanism. In an embodiment, the frame includes common reference sequences (CRS) for channel estimation. In an embodiment, the number of symbols in which the CRS is inserted is determined according to the number of physical antennas. In an embodiment, the frame includes a data demodulation reference sequences (DMRS). In an embodiment, the number of symbols in which the DMRS is inserted is determined according to the number of transmission streams.

Disclosed herein is a method in a wireless network device for receiving and decoding a mixed format frame. The method includes receiving a frame, wherein the frame that includes OFDM symbols in two different FFT sizes. The frame includes a first portion and a second portion, wherein the first portion includes a first FFT size and the second portion includes a second FFT size. The method also includes decoding the first portion according to the first FFT size, wherein the first portion is a preamble and decoding the second portion according to the second FFT size, wherein the second portion is a data portion of the frame.

FIG. 1 illustrates a network 100 for communicating data. The network 100 comprises an access point (AP) 110 having a coverage area 112, a plurality of user equipment (UEs) 120, and a backhaul network 130. As used herein, the term AP may also be referred to as a transmission point (TP) and the two terms may be used interchangeably throughout this disclosure. The AP 110 may comprise any component capable of providing wireless access by, inter alia, establishing uplink (dashed line) and/or downlink (dotted line) connections with the UEs 120, such as a base transceiver station (BTS), an enhanced base station (eNB), a femtocell, and other wirelessly enabled devices. The UEs 120 may comprise any component capable of establishing a wireless connection with the AP 110. The backhaul network 130 may be any component or collection of components that allow data to be exchanged between the AP 110 and a remote end (not shown). In some embodiments, the network 100 may comprise various other wireless devices, such as relays, femtocells, etc.

In an embodiment, the AP 110 is configured to transmit in a mixed OFDMA frame format. The mixed OFDMA frame format may be decodable by both legacy WLAN devices that are not otherwise compatible with newer wireless and WLAN protocols and new wireless devices configured for HEW standards. In an embodiment, the AP 110 is a cellular AP. In another embodiment, the AP 110 is a WiFi AP.

FIG. 2 illustrates various IEEE 802.11 architectures. In one example, a high efficiency WLAN system 200 is shown in a single basic service set (BSS) environment that contains a single AP 202 with a mix of legacy STAs 204 and HEW STAs 206. HEW increases the BSS overall throughput while supporting legacy STAs.

In another example, a second high efficiency WLAN system 250 is shown in an overlapping BSS (OBSS) environment, in which multiple APs 252, 258 supports their own BSSs (BSS 1 and BSS 2) with both mixed legacy STAs 254, 260 and HEW STAs 256, 262. HEW reduces the interference, increases the area throughput, and may include the support of legacy STAs 254, 260.

Various embodiments provide one or more of a frame format, reference sequences, and tone mapping for OFDMA WLAN. The frame structure is designed to support backward compatibility. An embodiment includes a mixed frame format. The frame control field in the frame format carries relatively important information such as MAP configuration, and it provides an auto-detection scheme as well. The auto-detection scheme allows a legacy device to stop decoding the HEW frame when the legacy device encounters this frame control field.

An embodiment includes a tone mapping per 20 megahertz (MHz), as the numerology is changed from 64 tones to 512 or 1024 tones per 20 MHz. As used herein the term numerology means the number of tones per OFDM symbol. The terms FFT size and numerology format are used interchangeably throughout this disclosure. While embodiments are described using a number of tones per 20 MHz as 512 or 1024, but there may be any number of tones.

An embodiment provides reference sequences (RSs) for channel estimation of OFDMA packets. The common RS (CRS) is designed for the beamforming report. The channel for all the subcarriers per symbol is estimated by all the participating devices in an OFDMA scheduler through the CRS. The data demodulation RS (DMRS) is used for the effective channel estimation of each STA, so the DMRS is designed per resource unit (RU). The DMRS patterns for STAs whose RUs are assigned with the different number of units may be different, based on the number of assigned RUs.

An embodiment includes a mixed frame structure that provides auto-detection functionality between legacy devices and HEW devices. An embodiment uses space-time block code (STBC) based quadrature phase shift keying (QPSK) or QPSK with a receiver diversity scheme for the frame control field. An embodiment includes reference sequence patterns designed for channel sounding and data demodulation. Embodiments may be implemented in legacy devices (e.g., 802.11n/ac devices) as well as HEW devices. Embodiments may be implemented in Wi-Fi enterprise, STAs, and APs.

Frame Format

As OFDMA technology sees increased usage in future generations of WLAN standards (e.g., 802.11 HEW), it is useful to provide a frame format that is backward compatible with legacy WLAN devices.

With respect to 20 MHz OFDMA transmission, FIG. 3 illustrates a mixed OFDMA frame 300 format with a HEW-data portion 310 having a numerology that may be different from the legacy WLAN portion 312. As used herein the term numerology means the number of tones per OFDM symbol. For example, in an embodiment, the HEW-data portion 310 may have 512 or 1024 tones per 20 MHz symbol, and the OFDM portion 312 with the legacy numerology may have 64 tones per 20 MHz symbol. In other embodiments, the HEW-data portion 310 may have a different number of tones per 20 MHz symbol other than 512 or 1024. In other embodiments, the mixed OFDMA frame 300 may be transmitted in a different frequency from 20 MHz.

In an embodiment, the frame format 300 includes a HEW-data portion 310 and a legacy portion 312. The legacy portion 312 includes legacy preamble elements such as the legacy short training field (L-STF) 302, the legacy long training field (L-LTF) 304, and the legacy signal field (L-SIG) 306 which are a legacy preamble portion of the frame 300. All devices, including legacy devices, may use the preamble portion of the frame 300 to determine the frame length. In an embodiment, the L-STF is about 2 symbols, the L-LTF is 2 symbols, the L-SIG 306 is 1 symbol, and the frame control field 308 is 2 symbols. In other embodiments, the number of symbols that comprise each of the L-STF 302, the L-LTF 304, the L-SIG 306, and the frame control field 308 may be different from that shown and described in FIG. 3. In an embodiment, while the L-SIG 306 provides the length information of the frame, the L-STF 302 and L-LTF 304 provide the synchronization and channel estimation for the OFDMA HEW-data portion 310 as well as for the legacy portion 312. The frame control symbols 308 carry information used for OFDMA data transmission, such as downlink/uplink (DL/UL) MAP configuration, DL/UL acknowledgement (ACK) configuration, etc. The frame control symbols 308 also become a transition period between the legacy portion 312 and the HEW-data portion 310. IEEE 802.11ac and 802.11n devices (i.e., legacy devices) stop decoding when they encounter frame control symbols 308 that are differently modulated, using an auto-detection mechanism. The frame control symbols 308 can be QPSK modulated, so the frame control symbols carry more information bits compared to the binary phase-shift keying (BPSK) modulated symbols. A HEW device can have at least two receiver (RX) antennas, and the RX diversity may be applied in receiving the signal. This can aid in achieving the same reliable communication as the current legacy SIG field transmission modulated in BPSK without the RX diversity. Those QPSK modulated frame control symbols provide the auto-detection functionality, and the legacy devices stop decoding the frame as they encounter the differently modulated frame control symbols.

FIG. 4 illustrates a mixed OFDMA frame format 400 with STBC based frame control symbols. Frame format 400 includes a legacy portion 414 and a HEW-data portion 412. The legacy portion 414 includes L-STF 402, L-LTF 404, L-SIG field 406, L-LTF1 408, and a frame control field 410. In an embodiment, the L-STF 402 may be 2 symbols, the L-LTF 404 may be 2 symbols, the L-SIG 406 may be 1 symbol, the L-LTF1 408 may be 1 symbol, and the frame control field 410 may be 2 symbols. In other embodiments, the symbol lengths for the fields L-STF 402, L-LTF 404, L-SIG 406, the L-LTF1 408, and the frame control field 410 may be different from those described and shown in FIG. 4. In an embodiment, one OFDM symbol, that is, L-LTF1 408 in FIG. 4, is inserted to enable the STBC-based frame control symbols to be decoded at the RX. One LTF from the L-LTF symbols 404 and another with L-LTF1 408 are used to estimate the two stream channels for two streams STBC, that is, the Alamouti Scheme, to be decoded at the RX. Because the reliability of the packet transmission is achieved with the STBC, the frame control symbols may be modulated with QPSK, and the L-LTF1 408 and the first symbol of frame control symbols 410 with QPSK modulation make an auto-detection between the legacy devices and the HEW devices. That is, the legacy devices stop decoding the frame when they are encountered with the L-LTF1 408 and the first symbol of the frame control symbols 410.

Tone Mapping for the OFDMA Symbol with 512 Tones Per 20 MHz Symbol

In using 512 tones for a 20 MHz OFDM/OFDMA symbol in a WLAN system, an embodiment sets the guard band and DC null subcarriers. An embodiment sets the first 23 tones and the last 22 tones aside for the guard band purpose, and also sets the 256^(th), 257^(th), and 258^(th) subcarriers aside for the DC nulls. That is, among the subcarriers with the index 0 to 511, the index 0 to 22 and 490 to 511 are guard band tones, and the tone indexes 255, 256 and 257 are set aside for the DC nulls.

Common Reference Sequence Pattern

In an embodiment, the common reference sequence (CRS) used for channel estimation of the multiple actual physical antennas between the TX and the RX in the OFDMA data portion has the following patterns. CRS is used for channel sounding, which is used for beam-forming feedback.

The location of the LTS in the L-LTF is reused for positioning the CRS of the new OFDMA symbol, and the L-LTF is one of the CRS for the OFDMA symbol.

Table 1 illustrates an embodiment CRS pattern.

TABLE 1 using L-LTF OFDMA-1 OFDMA-2 OFDMA-3 OFDMA-4 OFDMA-5 OFDMA-6 OFDMA-7 0 GB GB GB GB GB GB GB GB 1 GB GB GB GB GB GB GB GB 2 GB GB GB GB GB GB GB GB 3 GB GB GB GB GB GB GB GB 4 GB GB GB GB GB GB GB GB 5 GB GB GB GB GB GB GB GB 6 GB GB GB GB GB GB GB GB 7 GB GB GB GB GB GB GB GB 8 GB GB GB GB GB GB GB GB 9 GB GB GB GB GB GB GB GB 10 GB GB GB GB GB GB GB GB 11 GB GB GB GB GB GB GB GB 12 GB GB GB GB GB GB GB GB 13 GB GB GB GB GB GB GB GB 14 GB GB GB GB GB GB GB GB 15 GB GB GB GB GB GB GB GB 16 GB GB GB GB GB GB GB GB 17 GB GB GB GB GB GB GB GB 18 GB GB GB GB GB GB GB GB 19 GB GB GB GB GB GB GB GB 20 GB GB GB GB GB GB GB GB 21 GB GB GB GB GB GB GB GB 22 GB GB GB GB GB GB GB GB 23 24 25 26 27 28 29 30 31 32 1 1 1 1 1 1 1 1 33 34 35 36 37 38 39 40 1 1 1 1 1 1 1 1 41 42 43 44 45 46 47 48 1 1 1 1 1 1 1 1 49 50 51 52 53 54 55 56 1 1 1 1 1 1 1 1 57 58 59 60 61 62 63 64 −1 −1 −1 −1 −1 −1 −1 −1 65 66 67 68 69 70 71 72 −1 −1 −1 −1 −1 −1 −1 −1 73 74 75 76 77 78 79 80 1 1 1 1 1 1 1 1 81 82 83 84 85 86 87 88 1 1 1 1 1 1 1 1 89 90 91 92 93 94 95 96 −1 −1 −1 −1 −1 −1 −1 −1 97 98 99 100 101 102 103 104 1 1 1 1 1 1 1 1 105 106 107 108 109 110 111 112 −1 −1 −1 −1 −1 −1 −1 −1 113 114 115 116 117 118 119 120 1 1 1 1 1 1 1 1 121 122 123 124 125 126 127 128 1 1 1 1 1 1 1 1 129 130 131 132 133 134 135 136 1 1 1 1 1 1 1 1 137 138 139 140 141 142 143 144 1 1 1 1 1 1 1 1 145 146 147 148 149 150 151 152 1 1 1 1 1 1 1 1 153 154 155 156 157 158 159 160 1 1 1 1 1 1 1 1 161 162 163 164 165 166 167 168 −1 −1 −1 −1 −1 −1 −1 −1 169 170 171 172 173 174 175 176 −1 −1 −1 −1 −1 −1 −1 −1 177 178 179 180 181 182 183 184 1 1 1 1 1 1 1 1 185 186 187 188 189 190 191 192 1 1 1 1 1 1 1 1 193 194 195 196 197 198 199 200 −1 −1 −1 −1 −1 −1 −1 −1 201 202 203 204 205 206 207 208 1 1 1 1 1 1 1 1 209 210 211 212 213 214 215 216 −1 −1 −1 −1 −1 −1 −1 −1 217 218 219 220 221 222 223 224 1 1 1 1 1 1 1 1 225 226 227 228 229 230 231 232 1 1 1 1 1 1 1 1 233 234 235 236 237 238 239 240 1 1 1 1 1 1 1 1 241 242 243 244 245 246 247 248 1 1 1 1 1 1 1 1 249 250 251 252 253 254 255 Null Null Null Null Null Null Null Null 256 DC DC DC DC DC DC DC DC 257 Null Null Null Null Null Null Null Null 258 259 260 261 262 263 264 1 1 1 1 1 1 1 1 265 266 267 268 269 270 271 272 −1 −1 −1 −1 −1 −1 −1 −1 273 274 275 276 277 278 279 280 −1 −1 −1 −1 −1 −1 −1 −1 281 282 283 284 285 286 287 288 1 1 1 1 1 1 1 1 289 290 291 292 293 294 295 296 1 1 1 1 1 1 1 1 297 298 299 300 301 302 303 304 −1 −1 −1 −1 −1 −1 −1 −1 305 306 307 308 309 310 311 312 1 1 1 1 1 1 1 1 313 314 315 316 317 318 319 320 −1 −1 −1 −1 −1 −1 −1 −1 321 322 323 324 325 326 327 328 1 1 1 1 1 1 1 1 329 330 331 332 333 334 335 336 −1 −1 −1 −1 −1 −1 −1 −1 337 338 339 340 341 342 343 344 −1 −1 −1 −1 −1 −1 −1 −1 345 346 347 348 349 350 351 352 −1 −1 −1 −1 −1 −1 −1 −1 353 354 355 356 357 358 359 360 −1 −1 −1 −1 −1 −1 −1 −1 361 362 363 364 365 366 367 368 −1 −1 −1 −1 −1 −1 −1 −1 369 370 371 372 373 374 375 376 1 1 1 1 1 1 1 1 377 378 379 380 381 382 383 384 1 1 1 1 1 1 1 1 385 386 387 388 389 390 391 392 −1 −1 −1 −1 −1 −1 −1 −1 393 394 395 396 397 398 399 400 −1 −1 −1 −1 −1 −1 −1 −1 401 402 403 404 405 406 407 408 1 1 1 1 1 1 1 1 409 410 411 412 413 414 415 416 −1 −1 −1 −1 −1 −1 −1 −1 417 418 419 420 421 422 423 424 1 1 1 1 1 1 1 1 425 426 427 428 429 430 431 432 −1 −1 −1 −1 −1 −1 −1 −1 433 434 435 436 437 438 439 440 1 1 1 1 1 1 1 1 441 442 443 444 445 446 447 448 1 1 1 1 1 1 1 1 449 450 451 452 453 454 455 456 1 1 1 1 1 1 1 1 457 458 459 460 461 462 463 464 1 1 1 1 1 1 1 1 465 466 467 468 469 470 471 472 −1 −1 −1 −1 −1 −1 −1 −1 473 474 475 476 477 478 479 480 −1 −1 −1 −1 −1 −1 −1 −1 481 482 483 484 485 486 487 488 489 490 GB GB GB GB GB GB GB GB 491 GB GB GB GB GB GB GB GB 492 GB GB GB GB GB GB GB GB 493 GB GB GB GB GB GB GB GB 494 GB GB GB GB GB GB GB GB 495 GB GB GB GB GB GB GB GB 496 GB GB GB GB GB GB GB GB 497 GB GB GB GB GB GB GB GB 498 GB GB GB GB GB GB GB GB 499 GB GB GB GB GB GB GB GB 500 GB GB GB GB GB GB GB GB 501 GB GB GB GB GB GB GB GB 502 GB GB GB GB GB GB GB GB 503 GB GB GB GB GB GB GB GB 504 GB GB GB GB GB GB GB GB 505 GB GB GB GB GB GB GB GB 506 GB GB GB GB GB GB GB GB 507 GB GB GB GB GB GB GB GB 508 GB GB GB GB GB GB GB GB 509 GB GB GB GB GB GB GB GB 510 GB GB GB GB GB GB GB GB 511 GB GB GB GB GB GB GB GB

The first 7 OFDMA symbols are supposed to have the CRS, and the CRS pattern is the repetition of the LTS pattern in the L-LTF. The LTS of the L-LTF is a part of CRS, and including this, the total 8×8 MIMO configuration can be sounded. However, embodiments are not limited to the 8×8 MIMO sounding, but may be extended to any number of MIMO configuration, such as by adding more OFDMA symbols with the CRS inserted (e.g. as for 12×12 MIMO, 4 more OFDMA symbols, in addition to the existing CRS, have the CRS).

Data Demodulation Reference Sequence Pattern

While the number of symbols into which the CRS is inserted is determined with the number of physical antennas, the number of symbols into which the data demodulation reference sequences (DMRS) is inserted depends on the number of TX streams. In particular, each STA is likely to have a different beam-forming applied in the transmission, and thus the pilot pattern is a resource unit (RU) (8 subcarriers×8 symbols) based design and the number of TX streams is indicated by the scheduler (which can be an AP in the WLAN system) in the DL/UL MAP.

An embodiment sets the different DMRS patterns in accordance with the number of RUs assigned per STA. The document attached hereto labeled CRS-DMRS shows the DMRS pattern for the case of 1 RU per STA. The CRS patterns are reused on the DMRS patterns, and new DMRS pilots are inserted. Those pilots labeled new DMRS are the newly inserted DMRS pilots in addition to the reused CRS pilots.

Table 2 illustrates a DMRS pattern for 3 RUs per STA and Table 3 illustrates a DMRS pattern for 4 RUs per STA.

TABLE 2 using L-LTF OFDMA-1 OFDMA-2 OFDMA-3 OFDMA-4 OFDMA-5 OFDMA-6 OFDMA-7 0 GB GB GB GB GB GB GB GB 1 GB GB GB GB GB GB GB GB 2 GB GB GB GB GB GB GB GB 3 GB GB GB GB GB GB GB GB 4 GB GB GB GB GB GB GB GB 5 GB GB GB GB GB GB GB GB 6 GB GB GB GB GB GB GB GB 7 GB GB GB GB GB GB GB GB 8 GB GB GB GB GB GB GB GB 9 GB GB GB GB GB GB GB GB 10 GB GB GB GB GB GB GB GB 11 GB GB GB GB GB GB GB GB 12 GB GB GB GB GB GB GB GB 13 GB GB GB GB GB GB GB GB 14 GB GB GB GB GB GB GB GB 15 GB GB GB GB GB GB GB GB 16 GB GB GB GB GB GB GB GB 17 GB GB GB GB GB GB GB GB 18 GB GB GB GB GB GB GB GB 19 GB GB GB GB GB GB GB GB 20 GB GB GB GB GB GB GB GB 21 GB GB GB GB GB GB GB GB 22 GB GB GB GB GB GB GB GB 23 24 1 1 1 1 1 1 1 1 New-DMRS 25 26 27 28 29 1 1 1 1 1 1 1 1 New-DMRS 30 31 Same 32 1 1 1 1 1 1 1 1 1 CRS STA 33 34 35 36 37 38 39 40 1 1 1 1 1 1 1 1 1 CRS 41 42 43 44 45 46 47 48 1 1 1 1 1 1 1 1 1 CRS 49 50 51 52 53 1 1 1 1 1 1 1 1 New-DMRS 54 55 Same 56 1 1 1 1 1 1 1 1 1 CRS STA 57 58 59 60 61 62 63 64 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 65 66 67 68 69 70 71 72 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 73 74 75 76 77 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 78 79 Same 80 1 1 1 1 1 1 1 1 1 CRS STA 81 82 83 84 85 86 87 88 1 1 1 1 1 1 1 1 1 CRS 89 90 91 92 93 94 95 96 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 97 98 99 100 101 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 102 103 Same 104 1 1 1 1 1 1 1 1 1 CRS STA 105 106 107 108 109 110 111 112 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 113 114 115 116 117 118 119 120 1 1 1 1 1 1 1 1 1 CRS 121 122 123 124 125 1 1 1 1 1 1 1 1 New-DMRS 126 127 Same 128 1 1 1 1 1 1 1 1 1 CRS STA 129 130 131 132 133 134 135 136 1 1 1 1 1 1 1 1 1 CRS 137 138 139 140 141 142 143 144 1 1 1 1 1 1 1 1 1 CRS 145 146 147 148 149 1 1 1 1 1 1 1 1 New-DMRS 150 151 Same 152 1 1 1 1 1 1 1 1 1 CRS STA 153 154 155 156 157 158 159 160 1 1 1 1 1 1 1 1 1 CRS 161 162 163 164 165 166 167 168 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 169 170 171 172 173 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 174 175 Same 176 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS STA 177 178 179 180 181 182 183 184 1 1 1 1 1 1 1 1 1 CRS 185 186 187 188 189 190 191 192 1 1 1 1 1 1 1 1 1 CRS 193 194 195 196 197 1 1 1 1 1 1 1 1 New-DMRS 198 199 Same 200 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS STA 201 202 203 204 205 206 207 208 1 1 1 1 1 1 1 1 1 CRS 209 210 211 212 213 214 215 216 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 217 218 219 220 221 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 222 223 Same 224 1 1 1 1 1 1 1 1 1 CRS STA 225 226 227 228 229 230 231 232 1 1 1 1 1 1 1 1 1 CRS 233 234 235 236 237 238 239 240 1 1 1 1 1 1 1 1 1 CRS 241 242 243 244 245 1 1 1 1 1 1 1 1 New-DMRS 246 247 248 1 1 1 1 1 1 1 1 1 CRS 249 250 251 252 253 1 1 1 1 1 1 1 1 New-DMRS 254 255 Null Null Null Null Null Null Null Null 256 DC DC DC DC DC DC DC DC 257 Null Null Null Null Null Null Null Null 258 259 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 260 261 262 263 264 1 1 1 1 1 1 1 1 1 CRS 265 266 Same 267 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS STA 268 269 270 271 272 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 273 274 275 276 277 278 279 280 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 281 282 283 284 285 286 287 288 1 1 1 1 1 1 1 1 1 CRS 289 290 Same 291 1 1 1 1 1 1 1 1 New-DMRS STA 292 293 294 295 296 1 1 1 1 1 1 1 1 1 CRS 297 298 299 300 301 302 303 304 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 305 306 307 308 309 310 311 312 1 1 1 1 1 1 1 1 1 CRS 313 314 Same 315 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS STA 316 317 318 319 320 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 321 322 323 324 325 326 327 328 1 1 1 1 1 1 1 1 1 CRS 329 330 331 332 333 334 335 336 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 337 338 Same 339 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS STA 340 341 342 343 344 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 345 346 347 348 349 350 351 352 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 353 354 355 356 357 358 359 360 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 361 362 Same 363 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS STA 364 365 366 367 368 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 369 370 371 372 373 374 375 376 1 1 1 1 1 1 1 1 1 CRS 377 378 379 380 381 382 383 384 1 1 1 1 1 1 1 1 1 CRS 385 386 Same 387 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS STA 388 389 390 391 392 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 393 394 395 396 397 398 399 400 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 401 402 403 404 405 406 407 408 1 1 1 1 1 1 1 1 1 CRS 409 410 Same 411 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS STA 412 413 414 415 416 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 417 418 419 420 421 422 423 424 1 1 1 1 1 1 1 1 1 CRS 425 426 427 428 429 430 431 432 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 433 434 Same 435 1 1 1 1 1 1 1 1 New-DMRS STA 436 437 438 439 440 1 1 1 1 1 1 1 1 1 CRS 441 442 443 444 445 446 447 448 1 1 1 1 1 1 1 1 1 CRS 449 450 451 452 453 454 455 456 1 1 1 1 1 1 1 1 1 CRS 457 458 Same 459 1 1 1 1 1 1 1 1 New-DMRS STA 460 461 462 463 464 1 1 1 1 1 1 1 1 1 CRS 465 466 467 468 469 470 471 472 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 473 474 475 476 477 478 479 480 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 481 482 483 1 1 1 1 1 1 1 1 New-DMRS 484 485 486 487 488 1 1 1 1 1 1 1 1 New-DMRS 489 490 GB GB GB GB GB GB GB GB 491 GB GB GB GB GB GB GB GB 492 GB GB GB GB GB GB GB GB 493 GB GB GB GB GB GB GB GB 494 GB GB GB GB GB GB GB GB 495 GB GB GB GB GB GB GB GB 496 GB GB GB GB GB GB GB GB 497 GB GB GB GB GB GB GB GB 498 GB GB GB GB GB GB GB GB 499 GB GB GB GB GB GB GB GB 500 GB GB GB GB GB GB GB GB 501 GB GB GB GB GB GB GB GB 502 GB GB GB GB GB GB GB GB 503 GB GB GB GB GB GB GB GB 504 GB GB GB GB GB GB GB GB 505 GB GB GB GB GB GB GB GB 506 GB GB GB GB GB GB GB GB 507 GB GB GB GB GB GB GB GB 508 GB GB GB GB GB GB GB GB 509 GB GB GB GB GB GB GB GB 510 GB GB GB GB GB GB GB GB 511 GB GB GB GB GB GB GB GB

TABLE 3 using L-LTF OFDMA-1 OFDMA-2 OFDMA-3 OFDMA-4 OFDMA-5 OFDMA-6 OFDMA-7 0 GB GB GB GB GB GB GB GB 1 GB GB GB GB GB GB GB GB 2 GB GB GB GB GB GB GB GB 3 GB GB GB GB GB GB GB GB 4 GB GB GB GB GB GB GB GB 5 GB GB GB GB GB GB GB GB 6 GB GB GB GB GB GB GB GB 7 GB GB GB GB GB GB GB GB 8 GB GB GB GB GB GB GB GB 9 GB GB GB GB GB GB GB GB 10 GB GB GB GB GB GB GB GB 11 GB GB GB GB GB GB GB GB 12 GB GB GB GB GB GB GB GB 13 GB GB GB GB GB GB GB GB 14 GB GB GB GB GB GB GB GB 15 GB GB GB GB GB GB GB GB 16 GB GB GB GB GB GB GB GB 17 GB GB GB GB GB GB GB GB 18 GB GB GB GB GB GB GB GB 19 GB GB GB GB GB GB GB GB 20 GB GB GB GB GB GB GB GB 21 GB GB GB GB GB GB GB GB 22 GB GB GB GB GB GB GB GB 23 24 1 1 1 1 1 1 1 1 New-DMRS 25 26 27 28 29 1 1 1 1 1 1 1 1 New-DMRS 30 31 32 1 1 1 1 1 1 1 1 1 CRS 33 34 35 36 37 1 1 1 1 1 1 1 1 New-DMRS 38 39 40 1 1 1 1 1 1 1 1 1 CRS 41 42 43 44 45 1 1 1 1 1 1 1 1 New-DMRS 46 47 48 1 1 1 1 1 1 1 1 1 CRS 49 50 51 52 53 1 1 1 1 1 1 1 1 New-DMRS 54 55 56 1 1 1 1 1 1 1 1 1 CRS 57 58 59 60 61 1 1 1 1 1 1 1 1 New-DMRS 62 63 64 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 65 66 67 68 69 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 70 71 72 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 73 74 75 76 77 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 78 79 80 1 1 1 1 1 1 1 1 1 CRS 81 82 83 84 85 1 1 1 1 1 1 1 1 New-DMRS 86 87 88 1 1 1 1 1 1 1 1 1 CRS 89 90 91 92 93 1 1 1 1 1 1 1 1 New-DMRS 94 95 96 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 97 98 99 100 101 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 102 103 104 1 1 1 1 1 1 1 1 1 CRS 105 106 107 108 109 1 1 1 1 1 1 1 1 New-DMRS 110 111 112 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 113 114 115 116 117 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 118 119 120 1 1 1 1 1 1 1 1 1 CRS 121 122 123 124 125 1 1 1 1 1 1 1 1 New-DMRS 126 127 128 1 1 1 1 1 1 1 1 1 CRS 129 130 131 132 133 1 1 1 1 1 1 1 1 New-DMRS 134 135 136 1 1 1 1 1 1 1 1 1 CRS 137 138 139 140 141 1 1 1 1 1 1 1 1 New-DMRS 142 143 144 1 1 1 1 1 1 1 1 1 CRS 145 146 147 148 149 1 1 1 1 1 1 1 1 New-DMRS 150 151 152 1 1 1 1 1 1 1 1 1 CRS 153 154 155 156 157 1 1 1 1 1 1 1 1 New-DMRS 158 159 160 1 1 1 1 1 1 1 1 1 CRS 161 162 163 164 165 1 1 1 1 1 1 1 1 New-DMRS 166 167 168 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 169 170 171 172 173 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 174 175 176 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 177 178 179 180 181 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 182 183 184 1 1 1 1 1 1 1 1 1 CRS 185 186 187 188 189 1 1 1 1 1 1 1 1 New-DMRS 190 191 192 1 1 1 1 1 1 1 1 1 CRS 193 194 195 196 197 1 1 1 1 1 1 1 1 New-DMRS 198 199 200 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 201 202 203 204 205 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 206 207 208 1 1 1 1 1 1 1 1 1 CRS 209 210 211 212 213 1 1 1 1 1 1 1 1 New-DMRS 214 215 216 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 217 218 219 220 221 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 222 223 224 1 1 1 1 1 1 1 1 1 CRS 225 226 227 228 229 1 1 1 1 1 1 1 1 New-DMRS 230 231 232 1 1 1 1 1 1 1 1 1 CRS 233 234 235 236 237 1 1 1 1 1 1 1 1 New-DMRS 238 239 240 1 1 1 1 1 1 1 1 1 CRS 241 242 243 244 245 1 1 1 1 1 1 1 1 New-DMRS 246 247 248 1 1 1 1 1 1 1 1 1 CRS 249 250 251 252 253 1 1 1 1 1 1 1 1 New-DMRS 254 255 Null Null Null Null Null Null Null Null 256 DC DC DC DC DC DC DC DC 257 Null Null Null Null Null Null Null Null 258 259 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 260 261 262 263 264 1 1 1 1 1 1 1 1 1 CRS 265 266 267 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 268 269 270 271 272 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 273 274 275 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 276 277 278 279 280 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 281 282 283 1 1 1 1 1 1 1 1 New-DMRS 284 285 286 287 288 1 1 1 1 1 1 1 1 1 CRS 289 290 291 1 1 1 1 1 1 1 1 New-DMRS 292 293 294 295 296 1 1 1 1 1 1 1 1 1 CRS 297 298 299 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 300 301 302 303 304 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 305 306 307 1 1 1 1 1 1 1 1 New-DMRS 308 309 310 311 312 1 1 1 1 1 1 1 1 1 CRS 313 314 315 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 316 317 318 319 320 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 321 322 323 1 1 1 1 1 1 1 1 New-DMRS 324 325 326 327 328 1 1 1 1 1 1 1 1 1 CRS 329 330 331 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 332 333 334 335 336 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 337 338 339 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 340 341 342 343 344 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 345 346 347 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 348 349 350 351 352 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 353 354 355 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 356 357 358 359 360 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 361 362 363 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 364 365 366 367 368 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 369 370 371 1 1 1 1 1 1 1 1 New-DMRS 372 373 374 375 376 1 1 1 1 1 1 1 1 1 CRS 377 378 379 1 1 1 1 1 1 1 1 New-DMRS 380 381 382 383 384 1 1 1 1 1 1 1 1 1 CRS 385 386 387 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 388 389 390 391 392 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 393 394 395 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 396 397 398 399 400 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 401 402 403 1 1 1 1 1 1 1 1 New-DMRS 404 405 406 407 408 1 1 1 1 1 1 1 1 1 CRS 409 410 411 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 412 413 414 415 416 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 417 418 419 1 1 1 1 1 1 1 1 New-DMRS 420 421 422 423 424 1 1 1 1 1 1 1 1 1 CRS 425 426 427 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 428 429 430 431 432 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 433 434 435 1 1 1 1 1 1 1 1 New-DMRS 436 437 438 439 440 1 1 1 1 1 1 1 1 1 CRS 441 442 443 1 1 1 1 1 1 1 1 New-DMRS 444 445 446 447 448 1 1 1 1 1 1 1 1 1 CRS 449 450 451 1 1 1 1 1 1 1 1 New-DMRS 452 453 454 455 456 1 1 1 1 1 1 1 1 1 CRS 457 458 459 1 1 1 1 1 1 1 1 New-DMRS 460 461 462 463 464 1 1 1 1 1 1 1 1 1 CRS 465 466 467 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 468 469 470 471 472 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 473 474 475 −1 −1 −1 −1 −1 −1 −1 −1 New-DMRS 476 477 478 479 480 −1 −1 −1 −1 −1 −1 −1 −1 −1 CRS 481 482 483 1 1 1 1 1 1 1 1 New-DMRS 484 485 486 487 488 1 1 1 1 1 1 1 1 New-DMRS 489 490 GB GB GB GB GB GB GB GB 491 GB GB GB GB GB GB GB GB 492 GB GB GB GB GB GB GB GB 493 GB GB GB GB GB GB GB GB 494 GB GB GB GB GB GB GB GB 495 GB GB GB GB GB GB GB GB 496 GB GB GB GB GB GB GB GB 497 GB GB GB GB GB GB GB GB 498 GB GB GB GB GB GB GB GB 499 GB GB GB GB GB GB GB GB 500 GB GB GB GB GB GB GB GB 501 GB GB GB GB GB GB GB GB 502 GB GB GB GB GB GB GB GB 503 GB GB GB GB GB GB GB GB 504 GB GB GB GB GB GB GB GB 505 GB GB GB GB GB GB GB GB 506 GB GB GB GB GB GB GB GB 507 GB GB GB GB GB GB GB GB 508 GB GB GB GB GB GB GB GB 509 GB GB GB GB GB GB GB GB 510 GB GB GB GB GB GB GB GB 511 GB GB GB GB GB GB GB GB

When the 3 RUs in the frequency domain are aggregated and assigned for one STA, the DMRS overhead may be reduced by removing pilots from two RUs out of three consecutive RUs. The same principle also applies to the case of four consecutively aggregated RUs per STA. Pilots from 3 RUs out of 4 consecutive RUs may be removed in the frequency domain to reduce the DMRS overhead.

FIG. 5 is a flowchart of an embodiment of a method 500 for generating a frame with a mixed OFDMA frame format. The method 500 begins at block 502 where a wireless network component generates a first portion of a frame including a first FFT size (i.e., a first numerology format). At block 504, the wireless network component generates a second portion of the frame including a second FFT size (i.e., numerology format). At block 506, the second portion of the frame is appended to the end of the first portion of the frame. At block 508, the wireless network component transmits the frame during a single transmission opportunity, after which, the method 500 ends. In an embodiment, the method 500 may be encoded as a set of computer readable instructions and stored on a computer readable storage media that, when implemented by a data processing system, causes the data processing system to execute the method 500.

FIG. 6 is a flowchart of an embodiment of a method 600 for decoding a frame that includes a mixed OFDMA frame format. The method 600 begins at block 602 where a wireless network component receives a frame that includes a mixed OFDMA frame format. At block 604, the wireless network component decodes a first portion of the frame that includes a first FFT size or numerology format. At block 606, the wireless network component decodes a second portion of the frame that includes a second FFT size or numerology format, after which, the method 600 ends. In an embodiment, the method 600 may be encoded as a set of computer readable instructions and stored on a computer readable storage media that, when implemented by a data processing system, causes the data processing system to execute the method 600.

FIG. 7 is a flowchart of an embodiment of a method 700 for decoding with a legacy wireless device a frame that includes a mixed OFDMA frame format that includes a first portion of a frame in a first FFT size or numerology format and a second portion of the frame in a second FFT size or numerology format. The method 700 begins at block 702 where the legacy wireless device receives a frame that includes a mixed OFDMA frame format. At block 704, the legacy wireless device decodes a first portion of the frame that includes a first FFT size or numerology format and determines that the remainder of the frame is in a different format and refrains from decoding the remainder of the frame, after which, the method 700 ends. In an embodiment, the first portion of the frame comprises a legacy format preamble. In an embodiment, the method 700 may be encoded as a set of computer readable instructions and stored on a computer readable storage media that, when implemented by a data processing system, causes the data processing system to execute the method 700.

FIG. 8 is a block diagram of a processing system 800 that may be used for implementing the devices and methods disclosed herein. Specific devices may utilize all of the components shown, or only a subset of the components and levels of integration may vary from device to device. Furthermore, a device may contain multiple instances of a component, such as multiple processing units, processors, memories, transmitters, receivers, etc. The processing system 800 may comprise a processing unit 801 equipped with one or more input/output devices, such as a speaker, microphone, mouse, touchscreen, keypad, keyboard, printer, display, and the like. The processing unit 801 may include a central processing unit (CPU) 810, memory 820, a mass storage device 830, a network interface 850, an I/O interface 860, and an antenna circuit 870 connected to a bus 840. The processing unit 801 also includes an antenna element 875 connected to the antenna circuit.

The bus 840 may be one or more of any type of several bus architectures including a memory bus or memory controller, a peripheral bus, video bus, or the like. The CPU 810 may comprise any type of electronic data processor. The memory 820 may comprise any type of system memory such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous DRAM (SDRAM), read-only memory (ROM), a combination thereof, or the like. In an embodiment, the memory 820 may include ROM for use at boot-up, and DRAM for program and data storage for use while executing programs.

The mass storage device 830 may comprise any type of storage device configured to store data, programs, and other information and to make the data, programs, and other information accessible via the bus 840. The mass storage device 830 may comprise, for example, one or more of a solid state drive, hard disk drive, a magnetic disk drive, an optical disk drive, or the like.

The I/O interface 860 may provide interfaces to couple external input and output devices to the processing unit 801. The I/O interface 860 may include a video adapter. Examples of input and output devices may include a display coupled to the video adapter and a mouse/keyboard/printer coupled to the I/O interface. Other devices may be coupled to the processing unit 801 and additional or fewer interface cards may be utilized. For example, a serial interface such as Universal Serial Bus (USB) (not shown) may be used to provide an interface for a printer.

The antenna circuit 870 and antenna element 875 may allow the processing unit 801 to communicate with remote units via a network. In an embodiment, the antenna circuit 870 and antenna element 875 provide access to a wireless wide area network (WAN) and/or to a cellular network, such as Long Term Evolution (LTE), Code Division Multiple Access (CDMA), Wideband CDMA (WCDMA), and Global System for Mobile Communications (GSM) networks. In some embodiments, the antenna circuit 870 and antenna element 875 may also provide Bluetooth and/or WiFi connection to other devices.

The processing unit 801 may also include one or more network interfaces 850, which may comprise wired links, such as an Ethernet cable or the like, and/or wireless links to access nodes or different networks. The network interface 801 allows the processing unit 801 to communicate with remote units via the networks 880. For example, the network interface 850 may provide wireless communication via one or more transmitters/transmit antennas and one or more receivers/receive antennas. In an embodiment, the processing unit 801 is coupled to a local-area network or a wide-area network for data processing and communications with remote devices, such as other processing units, the Internet, remote storage facilities, or the like.

While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description. It is therefore intended that the appended claims encompass any such modifications or embodiments. 

What is claimed is:
 1. A method in a network component for transmitting a frame of two different fast Fourier transform (FFT) sizes, comprising: generating a frame, wherein the frame comprises orthogonal frequency-division multiplexing (OFDM) symbols in two different FFT sizes, wherein the frame comprises a first portion and a second portion, wherein the first portion comprises a first FFT size and the second portion comprises a second FFT size; and transmitting the frame during a single transmission opportunity.
 2. The method of claim 1, wherein the first portion comprises a preamble.
 3. The method of claim 2, wherein the preamble comprises a legacy format.
 4. The method of claim 1, wherein the frame comprises a first field and a second field, and wherein the first field provides automatic gain control (AGC) and synchronization and the second field provides synchronization and channel estimation.
 5. The method of claim 1, wherein the first portion comprises a first field and a second field that provide information enabling a receiver to estimate two stream channels for two stream space-time block code (STBC).
 6. The method of claim 1, wherein the first portion comprises a frame control field and wherein the frame control field comprises two symbols causing a legacy device to stop decoding the frame when encountered by an auto-detection mechanism.
 7. The method of claim 1, wherein the frame comprises common reference sequences (CRS) for channel estimation.
 8. The method of claim 7, wherein a number of symbols in which the CRS is inserted is determined according to a number of physical antennas.
 9. The method of claim 1, wherein the frame comprises a data demodulation reference sequences (DMRS).
 10. The method of claim 9, wherein a number of symbols in which the DMRS is inserted is determined according to a number of transmission streams.
 11. A wirelessly enabled network component, comprising: a processor; and a computer readable storage medium storing programming for execution by the processor, the programming including instructions to: generate a frame, wherein the frame comprises orthogonal frequency-division multiplexing (OFDM) symbols in two different fast Fourier transform (FFT) sizes, wherein the frame comprises a first portion and a second portion, wherein the first portion comprises a first FFT size and the second portion comprises a second FFT size; and transmit the frame during a single transmission opportunity.
 12. The wirelessly enabled network component of claim 11, wherein the first portion comprises a preamble.
 13. The wirelessly enabled network component of claim 12, wherein the preamble comprises a legacy format.
 14. The wirelessly enabled network component of claim 11, wherein the frame comprises a first field and a second field, and wherein the first field provides automatic gain control (AGC) and synchronization and the second field provides synchronization and channel estimation.
 15. The wirelessly enabled network component of claim 11, wherein the first portion comprises a first field and a second field that provide information enabling a receiver to estimate two stream channels for two stream space-time block code (STBC).
 16. The wirelessly enabled network component of claim 11, wherein the first portion comprises a frame control field and wherein the frame control field comprises two symbols causing a legacy device to stop decoding the frame when encountered by an auto-detection mechanism.
 17. The wirelessly enabled network component of claim 11, wherein the frame comprises common reference sequences (CRS) for channel estimation.
 18. The wirelessly enabled network component of claim 17, wherein a number of symbols in which the CRS is inserted is determined according to a number of physical antennas.
 19. The wirelessly enabled network component of claim 11, wherein the frame comprises a data demodulation reference sequences (DMRS).
 20. The wirelessly enabled network component of claim 19, wherein a number of symbols in which the DMRS is inserted is determined according to a number of transmission streams.
 21. A method in a wireless network device, comprising: receiving a frame, wherein the frame comprises orthogonal frequency-division multiplexing (OFDM) symbols in two different FFT sizes, wherein the frame comprises a first portion and a second portion, wherein the first portion comprises a first FFT size and the second portion comprises a second FFT size; decoding the first portion according to the first FFT size, wherein the first portion comprises a preamble; and decoding the second portion according to the second FFT size, wherein the second portion comprises a data portion.
 22. A wireless system, comprising: a transmitter; and a processor coupled to the transmitter, wherein the processor is configured to generate a frame, wherein the frame comprises orthogonal frequency-division multiplexing (OFDM) symbols in two different fast Fourier transform (FFT) sizes, wherein the frame comprises a first portion and a second portion, wherein the first portion comprises a first FFT size and the second portion comprises a second FFT size, and wherein the processor is further configured to cause the transmitter to transmit the frame during a single transmission opportunity.
 23. The system of claim 22, wherein the first portion comprises a preamble.
 24. The system of claim 23, wherein the preamble comprises a legacy format.
 25. The system of claim 22, wherein the frame comprises a first field and a second field, and wherein the first field provides automatic gain control (AGC) and synchronization and the second field provides synchronization and channel estimation.
 26. The system of claim 22, wherein the first portion comprises a first field and a second field that provide information enabling a receiver to estimate two stream channels for two stream space-time block code (STBC).
 27. The system of claim 22, wherein the first portion comprises a frame control field and wherein the frame control field comprises two symbols causing a legacy device to stop decoding the frame when encountered by an auto-detection mechanism.
 28. The system of claim 22, wherein the frame comprises common reference sequences (CRS) for channel estimation.
 29. The system of claim 28, wherein a number of symbols in which the CRS is inserted is determined according to a number of physical antennas.
 30. The system of claim 22, wherein the frame comprises a data demodulation reference sequences (DMRS).
 31. The system of claim 30, wherein a number of symbols in which the DMRS is inserted is determined according to a number of transmission streams. 